The present invention relates to an apparatus for supplying powder, more specifically a powdery steel refining material, to a mold for continuous steel casting, that is, for spraying such material over the surface of molten metal in the mold.
There have been proposed a variety of methods of supplying powder to the mold. However, any such methods are not successful enough, because problems arise in the storing and transportation of powder and the condition of the supplied powder, particularly production of dust and uneven distribution thereof, and therefore none of the proposed methods have been used commercially. In practice, powder is supplied manually from the side of the mold by using rakes.
Moreover, such manual supply is done under very bad operating conditions, such as high temperature and space filled with dust. Therefore, there is a serious need for a method or apparatus which uses human hands as little as possible to be invented at the earliest possible date. A powder supplying apparatus is equipped, without exception, with a pneumatic powder-conveyor, which contains a powder supplying nozzle as a component. As for the powder supplying nozzle, it should function well to provide an even distribution of powder over the surface of molten metal in the mold, in such manner that choking of the nozzles and production of dust clouds are completely prevented, and observation of the surface of molten metal is made easy.
The powder supplying nozzles of the conventional type, for example are a pipe having simply a great number of holes in the longitudinal direction, but with variations in the number of holes; or are a pipe having a slit extending in the longitudinal direction. All these nozzles are positioned right above the surface of molten metal, constituting an obstacle to the observation or like work during the performance of the abovementioned function. Moreover, where the mold has a casting cross-section for casting a slab or a like shape which is flat, the nozzle must be moved horizontally in the long direction of the mold over the surface of molten metal by using a complicated driving mechanism, resulting in production of a dust cloud. Thus, it is difficult to properly lubricate the junction between the solidified shell of steel castings and the surface of the inside wall of the mold for the prevention of damage to the solidified shell and to collect floating slag on the surface of molten metal and maintain the temperature of the molten metal for producing pure steel.
In regard to the pneumatic powder-conveyor for supplying the mold, that is, pneumatically convey and spraying over the surface of molten metal in the mold, a powder, and more specifically a powdery refining material, conventionally used with the continuous casting apparatus, it is so designed from the standpoint of the layout of the necessary equipment on the working floor and for a greater availability of working space, that powder is pneumatically conveyed from the powder hopper and the conveying gas supply installed far from the mold through the main pneumatic powder-conveying pipe running to the mold, and is sprayed from the powder supplying nozzle which is connected at the end of said main pipe and positioned above the surface of molten metal in the mold.
Because the pneumatic powder-conveying main pipe is long as mentioned above, there is a posibility of build-up of powder in the main pipe after all the required powder has been conveyed and if conveying is interrupted, making it difficult to obtain smooth conveyance to the mold following an interruption or causing the pipe to be blocked at the worst.